Most combustion processes have, in some way or another, a recirculating flow field. The recirculating flow field tends to stabilize the combustion reaction zone, but an unnecessarily large recirculation zone can result in high nitrogen oxide (NOx) emissions for combustion systems.
Lean direct injection for combustion has been shown to have the potential to reduce NOx emissions. However, constructing a combustor to simply and uniformly inject many fuel and air streams presents a challenge. Non-premixed combustors typically use multiple fuel passages to inject fuel from a diffusion tip into air passing through an outer ring of the diffuser tip. This requires multiple diffuser tips with multiple separate air and fuel passages all mounted in a complicated head end assembly.
The shell and tube LDI combustion system of the present invention provides a means for easily constructing a combustion system made up of many LDI injector sets with uniform air and fuel flow through all the passages using a concept similar to a shell and tube heat exchanger design. A shell and tube heat exchanger consists of a shell with a bundle of tubes inside it. One fluid flows through the tubes and another fluid flows over the tubes, through the shell, to transfer heat between the two fluids.